How to Identify a Meteorite
(What you saw when you found it)

You say that you saw the rock fall from the sky. Are you sure?

Meteors enter the Earth's atmosphere at speeds ranging from 14 kilometers/second (31,000 miles per hour) to 45 kilometers per second (100,000 miles per hour). At first they burn on the surface and perhaps explode from the shock. But as they go farther into the atmosphere they slow down. All but the largest meteors (like the one that formed Meteor Crater) quit burning and fall dark from an altitude of from 5 to 20 km (3.2 to 12.4 miles). That's a long fall. No human can trace the fall of a rock that far. In fact, no human can even see a small rock at that distance. Where meteorites have been observed to fall, there has simply been a whoosh and a thunk.

By the time meteorites hit the earth they are traveling at terminal velocity--that is a velocity at which the resistance of the air will not let them go any faster. They are falling no faster than a rock dropped from an airplane--or the Coke bottle in the first scene "Gods Must Be Crazy." Terminal velocity for a small object is not very high--150 to 300 km/hr (100 to 200 miles per hour more or less) or less. These impacts don't make big craters. You are more likely to see a small indentation in the ground, a small hole, or nothing.

With this in mind, here is the bad news:

Many people report that a friend or relative (often an ancestor) saw the rock fall. Are you sure? Stories get told and retold . . . and changed. Old hoaxes or tall tales designed to entertain the grandchildren metamorphose into . . . truth. Well, not exactly.

Did you hear a whoosh and a thunk? Go here for the next test.

You didn't hear a whoosh and a thunk, but you still think you have a meteorite? Click here.



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